Learn About the Various Stages of Sleep

You may think that your brain goes into a passive or ‘shutdown’ mode when you go to sleep, but it’s actually quite active while you are catching some zzz’s. When you sleep, your brain goes through various stages of activity during 2 main sleep cycles – REM & Non-REM sleep. Take a look at what happens during each sleep stage below.

Non-REM Sleep – Stages 1-3

Non-REM, or NREM sleep stands for non-rapid eye movement & accounts for the first 3 stages of sleep. Non-REM sleep is also dreamless sleep, and during this part of the sleep cycle, the mind rests while your body heals.

Stage 1

The lightest stage of sleep and occurs seconds to minutes after nodding off. Stage 1 is often characterized by the presence of slow eye movements. During this stage, you’re still somewhat alert & can be easily woken. This is also the stage where some people experience hypnic jerks, in which a falling sensation is followed by a muscle jerk that brings you back into consciousness.

Stage 2

Almost half of time you spend asleep over the night is spent in Stage 2. Despite still being a lighter stage of sleep, your heart rate slows down & your core temperature decreases. During stage 2, eye movements also stop and your brain waves slow, but then produces sleep spindles, which are sudden increases in brain wave frequency. These bursts are thought to be a form of protection for the brain from awakening from sleep. 

Stage 3

This is the deep sleep stage, and serves as the most restorative stage of sleep. Arousals from stage 3 sleep are rare and it can be difficult to wake someone in this stage of sleep. During this stage, there is no eye movement, breathing becomes deeper & more rhythmic, and body movements tend to stop.

This stage aids in restoring & rejuvenating the body. Hormones are released during this stage that aid in restoring muscles & tissues that were exerted throughout the day. Your blood flow also increases, providing extra oxygen & nutrients to your muscles.

It is during this stage that parasomnias – such as sleepwaking, night terrors, & sleep talking – occur as well.

REM Sleep – Stage 4 

REM sleep stands for rapid-eye-movement, and it is the stage of sleep that you experience dreams. In general, most people fall into REM sleep 90minutes after falling sleep. Each REM stage can last up to 60 minutes, and the average adult has 5-6 REM cycles every night.

Your brain becomes more active during this final stage, heart rate & blood pressure increase, and your breathing becomes faster. REM sleep helps with memory and learning functions, as this is the stage where the brain processes & organizes information from the day before, and stores it for long-term memory.

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